Aggressive insulin therapy for tight glycemic control has been slow to gain acceptance in the clinical setting. One limitation is the inconvenience and poor subject acceptability of injection therapy, especially in a multiple daily injection regimen. In addition, the traditional dosing of pre-meal Regular insulin, 30 to 45 minutes before eating, to obtain optimal postprandial control is inconvenient. The present study is designed to evaluate pre-meal pulmonary delivery of insulin in subjects with diabetes mellitus poorly controlled on combination oral agents (sulfonylurea plus either metformin or troglitazone). The purpose is to determine: 1) whether add-on therapy with inhaled insulin significantly improves glycemic control as compared with continued oral agent therapy alone; 2)whether monotherapy with inhaled insulin significantly improves glycemic control as compared with continued oral agent therapy alone; 3) the toleration and safety of insulin therapy and its effects after 3 months, if any, on measures of pulmonary function.